A color filter is a major component of a liquid crystal display. A liquid crystal display relies on the color filter to exhibit colored images. During the operation of a liquid crystal display, the white light from a backlight is transmitted through a liquid crystal layer to the color filter. After the white light is transmitted through the red, green and blue subpixels of the color filter, red, green and blue light is formed and at last mixed together in human eyes to form colored images.
Conventional methods for manufacturing a color filter include printing, dyeing, pigment dispersion, electro-deposition, dry film method, and spraying that is used for large-sized panels. Currently, the pigment dispersion method is generally used in the industry. The most core process of this method relates to the technique of pigment dispersion. Since color photoresist has very high requirements on pigment particles, the particle sizes of the pigments usually have to be less than 100 nm, and moreover, the particle sizes have to be highly homogenous with a narrow distribution range. Currently, in the pigment dispersion technique, an oil phase solvent is used as the dispersion medium, and a proper dispersant system is chosen for grinding with high power dispersion instrument so as to achieve good dispersion.
In implementing the aforementioned pigment dispersion process with an oil phase solvent as the dispersion medium, the inventors have identified at least the following problems of this traditional technique: employment of a large amount of solvent results in volatile organic compounds (VOC) which is not environmentally friendly; the flammability and explosiveness of the solvent is adverse to workplace safety; and the solvent type color photoresist prepared from a solvent type pigment dispersion in use possesses an inherent deficiency that the viscosity is difficult to adjust exists. To obtain an operable viscosity, the molecular weight of the resin has to be controlled below a certain value, and therefore if the resin has a too high molecular weight, it requires a large amount of active diluent to dilute the resin, but this causes too high a crosslinking density and an increased brittleness of the prepared film, and the prepared film tends to shrink during solidification; if the molecular weight of the resin is too low, the requirement for hardness is difficult to satisfy. This causes an either “soft and flexible” or “hard and brittle” problem of the prepared film.